1. The Field of Invention
The present invention is directed to a cover for medical tubing. More particularly, the present invention relates to a medical tubing cover which encloses the ends of sterilized medical tubing and which can be easily removed from the tubing prior to use in surgical or other medical procedures.
2. The Prior Art
In recent years it has become increasingly popular to utilize pre-cut medical tubing packaged and sterilized within an airtight container. The container may be opened in the sterile field of the operating room and the medical tubing can be directly coupled into a fluid circuit without the need of measuring, cutting, or sterilizing the tubing. Thus, it will be appreciated that the availability of pre-cut, pre-sterilized medical tubing in a variety of lengths and diameters greatly simplifies the "scrub procedure" involved in constructing a fluid circuit.
It is well known in the art that it is desirable to enclose the ends of medical tubing after it has been sterilized so that the sterile condition may be maintained. Furthermore, in the case of the packaged medical tubing described above, it is desirable to provide covers at the ends of the medical tubing which (1) allow the sterilizing agent to pass through the tubing while it is within the airtight container, and which (2) preserve the aseptic condition of the medical tubing once the container is opened. Such covers, commonly referred to as "breather caps", are found in the prior art as described hereinafter.
The covers found in the prior art are typically injection molded having one closed end and the other end open so as to receive the end of the medical tubing in mating relationship. The walls of the prior art covers are tapered having a gradually reduced diameter so that, as the cover is advanced onto the tubing, the walls of the cover are stretched by the advancing tubing within the cover. This stretching action causes the outer surfaces of the tubing to come into contact with the inner wall surface of the cover, thereby "sealing" the end of the tubing.
In order to permit a sterilizing agent to pass through the tubing, it has been necessary to punch a hole in the closed end of the cover. However, this design is potentially dangerous. For example, it is not uncommon for the punched-out portion of the cover to remain loosely connected to the interior wall of the cover and then fall into the medical tubing between the time the tubing is packaged and used. Thus, it will be appreciated that the insoluble, punched-out portion of the cover could cause extreme complications if inadvertantly introduced into an extracaporeal fluid circuit.
Another disadvantage is that it is often difficult to remove the cover from the tubing prior to its use. This difficulty in removal is caused by the retention forces of the cover. Because the cover is stretched over the tubing, the retention forces are related to the elasticity of the material from which the cover is made. Furthermore, as the surface area of contact between the inner wall of the cover and the outer surface of the tubing increases, there is a substantial increase in the frictional forces. The prior art covers are even more difficult to remove because they are typically made from a "tacky" plastic material which has relatively high coefficient of friction.
To overcome these problems to a limited extent, covers are found in the prior art which utilize tapered walls and a plurality of spaced-apart ribs of uniform cross-sectional height located on the inner wall surfaces of the cover. Such a prior art cover is illustrated in FIGS. 1 and 2 of the drawing. It will be noted that since the ribs are relatively narrow, the surface area of contact between the inner wall of the cover and outer surface of the tubing is reduced, thereby minimizing the frictional forces.
However, while the use of such ribs provides some improvement over the previous designs, it will be appreciated that there still exists considerable retention forces since the wall of the cover must be stretched in order for the cover to be held in place. In fact, the prior art covers illustrated in FIGS. 1 and 2 have even higher retention forces because of the effective increase in the thickness of the wall, caused by the ribs. Great difficulty has therefore, been experienced in removing such covers. Since the purpose of these covers is to act as a sterile barrier, it is very important that they be secure without being too difficult to remove. When the covers are difficult to remove, technique errors, which compromise the sterility of the tubing, can occur.